Chart.js

let logsChartInstance = null;

async function loadLogs() {
  const user = auth.currentUser;
  if (!user) return;

  const snap = await db.collection("logs")
    .where("userId", "==", user.uid)
    .orderBy("date", "desc")
    .limit(30)
    .get();

  const logs = [];
  logsList.innerHTML = "";
  snap.forEach(doc => {
    const data = doc.data();
    logs.push(data);
    const li = document.createElement("li");
    li.textContent = `${data.date} - [${data.tag}] ${data.title}`;
    logsList.appendChild(li);
  });

  updateStreak(logs);
  drawLogsChart(logs);
}

// compute consecutive streak ending today
function updateStreak(logs) {
  const datesSet = new Set(logs.map(l => l.date));
  let streak = 0;
  let current = new Date();

  while (true) {
    const dStr = current.toISOString().slice(0,10);
    if (datesSet.has(dStr)) {
      streak++;
      current.setDate(current.getDate() - 1);
    } else {
      break;
    }
  }
  streakText.textContent = `Current streak: ${streak} day(s)`;
}

// Chart: count logs per day
function drawLogsChart(logs) {
  const byDate = {};
  logs.forEach(l => {
    byDate[l.date] = (byDate[l.date] || 0) + 1;
  });

  const labels = Object.keys(byDate).sort();
  const values = labels.map(d => byDate[d]);

  const ctx = document.getElementById("logsChart").getContext("2d");
  if (logsChartInstance) logsChartInstance.destroy();
  logsChartInstance = new Chart(ctx, {
    type: "bar",
    data: {
      labels,
      datasets: [{
        label: "Logs per day",
        data: values,
        backgroundColor: "rgba(37, 99, 235, 0.6)"
      }]
    }
  });
}